Antenna



o 30, 1951 N. E. LINDENBLAD 2,573,461

ANTENNA 1 Original Filed June 27, 1942-- Tlql.

' INVENTOR.

A TTOIWVE).

M46 .5 lavas/45440.

Patented Get. 30, 1951 ANTENNA Nils E. Lindenblad, Port J eflerson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application June 27, 1942, Serial No.

448,743, now Patent No. 2,414,266, dated January 14', 1947. Divided and this application December 12, 1946, Serial No. 715,824

20 Claims.

. 1 The present invention is a division of prior application Serial Number 448,743, filed June .27, 1942, now U. S. Patent 2,414,266, issued J anuary 14, 1947. j object of the present invention is the provision of a broad band broadcast antenna.

Another object of the present invention is the provision of a highly directive antenna having substantially all of its response pattern concentrated in a single lobe without secondary lobes. Still another object of'the present invention is the provision of a simple rugged antenna structure.

Still a further object of the present invention is the provision of a simple antenna structure which has no fragile projections which may be adversely aiiected by air flow thereabout or by weather conditions.

The foregoing objects and others which may appear from the following detailed description are attained by providing an antenna structure including a number of elongated quarter wave deep slots or pockets extending inwardly from a curved conductive sheet. The slots or pockets ,may have lengths of from one half to one operatstood by reference to the following detailed description which is accompanied by a drawing in which:

Figure 1 illustrates in an elevational view the application of the principles of the present invention to a broadcast antenna, while Figure 2 is a transverse section view of Figure 1 taken along lines 2, 2;

Figures 3 and 4 illustrate in transverse section a modification of the present invention particularly adapted for directional service, and

Figure 5 is a directivity pattern of the antenna shown in Figures 3 and 4.

The embodiment of the present invention shown in Figure 1 is particularly adapted for the broadcast transmission of short wave radiant energy. Its operation may be clearly understood by considering it to be constituted of a group of separate antennas stacked vertically one above the other to form an array. Each of the antennas of the array consist of a number of slots in conductive sheet 13 such as those identified in Figure 2 as 80, 8|, 82, 83, 84 and 85, each of the slots being spaced from the next a distance equal to a half of the operating wavelength. The slots antenna structure such as shown in Figure 3 may .be provided. structure 93 may be considered to be the nose of the body of a multi-engine airplane; It is here symmetrically arranged about a center line are 2 may have a length of from one half to one wavelength. Each of the slots to is closed on the inner side of the conductive sheet 13 by pockets 36 to 9| inclusive, each pocket or cavity having a depth equal to one quarter of the operating wavelength. The sheet 13 in which slots 80 to 85 are out is bent about a vertical axis of symmetry to form a cylinder. Thus there is obtained a simple sturdy structure electrically at ground potential and thoroughly protected against wind, weather and lightnin damage. The structure is particularly adapted for installation at the top of a tall building or tower such as that indicated by reference character 15. The antenna is energized by a plurality of transmission lines, only one of which, TL4, is shown in-Figure 2, the others being omitted in the interest of clarity. The outer conductor of transmission line T114 is connected to one side wall of pocket 9| with the central conductor passing across slot 85 and connected to its opposite edge. All the transmission lines energizing slots 80 to 85 inclusive may be connected in parallel to a main transmission line which is adapted'to be energized from a suitable source of high frequency energy. Impedance transformation for matching purposes may be obtained by adjustment of the distance away from the slot at which the transmission lines are connected across the respective cavities.

In certain types of installation of radio direction findin equipment in airplanes, it is particularly desirable to obtain alternately a pair of directivity patterns which are symmetrically disposed about a common axis along the line of flight of the plane and which overlap to considerable extent along the axis. This may be done with separate antennas or with a single antenna array alternately energized in two different ways. This effect may be obtained by utilizing the principles set forth in the prior application, Serial Number 448,743, filed June 27, 1942, issued January 14, 1947, as U. S. Patent 2,414,266 or as set forth with regard to Figures 1 and 2 of the present application. Thus, an

The curved conductive metallic shown. as though in horizontal cross section.

vertically disposed slots 94, 95, 96 and 91 spaced a half wave apart. The slots are closed within the body of the airplane by pockets I04, I05, I06 55 wavelength.

and Iflleach having a depth equal to a quarter Now, ifthis antenna structure is unsymducer equipment metry of the structure. If desired, the-directivity pattern of the antenna may be sharpened somewhat by providing parasitic half wave radiators I20 symmetrically disposed about the axis of symmetry of the antenna. They may be closely adjacent as shown in Figure 3, or more widely spaced so as to be bisected by the center lines of "slots 95 and 96 'as shown in Figure 4. Curve N of Figure illustrates the directivity pattern of the antenna shown in Figure 3 as energized by transmission line 'ZLi while curve H5 shows the 'directivity pattern of the antenna of Figure 4 similarly energized.

For the sake of convenience the foregoing description has been predicated on the assump- -tion that the antennas of the present invention are to be used for transmissionof radiant energy" waves.

It is to be clearly understood, however, that by connecting suitable receiving equipment to the transmission lines associated with the antennas reception of radiant energy waves may be accomplished.

What is-claimed is:

1. An antenna including a curved conductive sheet having a number of parallel slots therein, said slots being spaced apart a distance equal to ,a'hailf the operating wavelength, said slots being closed on one side by pockets having a depth equal to one .quarter of the operating wavelength .and means for connecting said antenna to transincludi-ng a two conductor transmission .line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to theother wall :of said pocket.

2. An antenna including a curved conductive sheet having a number of parallel slots therein, said slots being spaced apart a distance equal to :3 half the operating wavelength, said slots being parallel to the axis of curvature of said sheet, said slots ,being closed on one side by pockets having a depth equal to one quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected .to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket.

3. An antenna including a curved conductive "sheet having a number of parallel slots therein,

said slots being spaced apart a distance equal to a. half the operating wavelength and having a length of substantially one wavelength, said slots being parallel to the axis of curvature of said sheet, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket.

4. An antenna including a hollow conductive cylinder having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength, and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor con nected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket.

5. An antenna including a hollow conductive cylinder having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength, and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one-of said pockets and the other conductor passing through said pocket transverse to said slots and connected to the other wall of said pocket, said slots being arranged in a number of separate bands about said cylinder, all of said slots being energized in an in-phase relationship.

6. An antenna including a hollow conductive cylinder having a number of parallel slots therein, said slots being spaced apart a distance'equal to a half the operating wavelength and having a length of substantially one wavelengthsaid slots being parallel to the axis of said cylinder, said slots being closed on the interior of said cylinder by pockets having a depth equal to one quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket.

7. An antenna including a hollow conductive cylinder having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength and having a length of substantially one wavelength, said slots being parallel to the axis ofsaid cylinder, said slots being closed on the interior of said cylinder by pockets having a depth equal toone quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket, said slots being arranged in a number of separate bands about said cylinder, all of said slots being energized in an in-phase relationship.

8. An antenna including a curved conductive sheet having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength and parasitically energized directors operatively associated with some of said slots.

9. An antenna including a curved conductive sheet having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slots and connected to the other Wall of said pocket and parasitically energized directors operatively associated with some of said slots.

10. An antenna including a curved conductive sheet having a number of parallel slots therein, said slots being spaced apart a distance equal to a half the operating wavelength, said slots being parallel to the axis of curvature of said sheet, said slots being closed on one side by pockets having a depth equal to one quarter of the operating wavelength and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side wall of at least one of said pockets and the other conductor passing through said pocket transverse to said slot and connected to the other wall of said pocket and parasitically energized directors located transverse to and across some of said slots.

11. An antenna including a hollow conductive cylinder having a number of parallel elongated slots therein, said slots being arranged longitudinally of the axis of said cylinder and spaced apart a distance equal to a half the operating wavelength, and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side of at least one of said slots and the other conductor connected to the other side of said slot.

12. An antenna including a hollow conductive cylinder having a number of parallel elongated slots therein, said slots arranged longitudinally of the axis of said cylinder and being spaced apart a distance equal to a half the operating wavelength, and means for connecting said antenna to transducer equipment including a two conductor transmission line having one conductor connected to one side of at least one of said slots and the other conductor connected to the other side of said slot, said slots being arranged in a number of separate bands about said cylinder, all of said slots being energized in an in-phase relationship.

13. A broadcast antenna including a vertical conductive cylinder grounded at its base and having a circular cross section and having an elongated slot arranged vertically therein, said slot being closed at each end thereof, and a two conductor transmission line connected to opposite sides of said slot for energizing said antenna.

14. A broadcast antenna including a vertical conductive cylinder grounded at its base and having a circular cross section and having an elongated slot arranged vertically therein, said slot being closed at each end thereof and having a length between one half to one wavelength at the operating frequency, and a two conductor transmission line connected to opposite sides of said slot for energizing said antenna.

15. A broadcast antenna including a vertical conductive cylinder, said cylinder having a circular cross section and having a number of narrow elongated slots therein, said slots each being arranged longitudinally of the axis of said cylinder and having a length lying between one half to one wavelength at the operating frequency and means for coupling a two conductor transmission line in cophasal relationship to opposite sides of each of said slots for energizing said antenna.

16. A broadcast antenna including a conductive cylinder having a circular cross section and having a number of elongated slots therein, said slots being arranged longitudinally of the axis of said cylinder, and means for coupling a two conductor transmission line in cophasal relationship to opposite sides of each of said slots for energizing said antenna.

17. A short wave broadcast antenna system comprising a vertical metallic cylinder having a circular cross section, said cylinder being grounded at its lower end, three vertical, vertically aligned slots in said cylinder, each of said slots having a length substantially one-half to one wave length long at the desired operating frequency, a two conductor transmission line connected across said slots for exciting said antenna system whereby radiation takes place from the surface of said grounded cylinder by virtue of currents flowing in the surface of said cylinder in directions substantially at right angles to the length dimensions of said slots. i

18. An antenna including a hollow conductive cylinder having a number of parallel elongated slots arranged therein, said slots being arranged longitudinally of the axis of said cylinder and spaced apart a distance substantially equal to half of the operating wavelength, and conductive means individual to each of said slots connecting the edges of said slots to individual conductors of a two-conductor transmission line leading to transducer equipment.

19. An antenna comprising a vertical cylindrical metallic structure having a circular crosssection, said structure having a plurality of vertical slots aligned vertically therein, the base of said structure being grounded, each of said slots having a length between one half and one operating wavelength, and conductive means individual to each of said slots connecting opposing edges of said slots individually to the conductors of a two-conductive transmission line leading to transducer equipment.

20. A short wave broadcast antenna comprising a metal cylinder grounded at its lower end and having a circular cross-section, said cylinder having a plurality of vertically separated slots therein, each of said slots having a length between one half and one operating wavelength, and conductive means individual to said slots to connect opposing edges of said slots individually to the conductors of a two-conductor coaxial transmission line.

NILS E'. LINDENBLAD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain June 14, 1939 

